We have molecularly cloned (1), sequenced and expressed (2) the genes of the retrovirus associated with Acquired Immune Deficiency Syndrome (AIDS), and we have initiated genetic engineering approaches for the development and testing of subunit viral vaccines. The predicted sequence of the viral envelope (env) protein has been used to design synthetic peptides, and the entire env gene and various portions are to be cloned into bacterial, yeast, and mammalian expression vectors. Purified env polypeptides produced in these expression systems and synthetic peptides will be used to raise polyclonal antibodies in rabbits and subhuman primates and to raise monoclonal antibodies of mouse and human origin. Various adjuvants and antigen-presentation methods will be tested. Viral-specific antibodies will be evaluated in virus neutralization assays and in cytotoxicity assays. Cell-mediated immune responses will be assessed in sub-human primates. The form(s) of viral env antigen giving rise to the strongest and most durable measured immune responses will be used to immunize chimpanzees; these animals and cohort controls will be challenged with AIDS virus and protection from infection and disease will be assessed.